唯一|ゆいいつyuiitsu[1]atamadaka (head-high)

1. no-adjective, adverbonly; sole; unique
   初はじめの一いち歩ほが唯一ゆいいつの難関なんかん。↗

   The first step is the hardest.

• Synonym無二むにWrittenWritten/formal prose for peerless, matchless; mostly seen in 「唯一無二」 and 「無二の親友」, stressing how precious something is.
• Related不二ふじWrittenWritten/formal prose for peerless, one of a kind; also appears in letter closings and set phrases such as 「不二の名山」.
• Antonym多数たすうNeutralNeutral word for a large number or the majority; the opposite of 「唯一」, which means just one.

Use 「唯一」 when there is only one. To stress that something is unique and irreplaceable, use 「唯一無二」 or 「無二」. 「不二」 is formal written prose, also in letter closings; 「多数」 is the opposite, meaning many.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. それ以外いがいに同類どうるいの存在そんざいが認みとめられないこと。